Physical aggression and other indices of irritable affect have been consistently identified as potential risk factors for institutionalization and other negative care-related outcomes in patients with Alzheimer's disease and related conditions. A cohort of 255 persons with the clinical diagnosis of Alzheimer's disease, stratified on initial dementia severity level, will be prospectively studied over 12 months with a weekly surveillance protocol to capture specific episodes of physical aggression and situational factors. The descriptive aims of this study will be to characterize the number of persons with aggressive episodes and the rate of these episodes over 12 months as a function of initial level of cognitive impairment. In addition, the study will quantitatively describe six situational factors related to aggressive episodes. The study will test the hypotheses that, among patients with Alzheimer's disease, the presence of each of these factors predicts episodes of aggression: severe cognitive impairment, premorbid episodes of aggression, and severity of other behavioral disturbances. In addition, the data will permit testing the hypothesis that the presence and frequency of aggressive episodes predicts increased levels of emotional distress in the primary caregiver.